Results in Journal Nanotechnology: 20,646
(searched for: journal_id:(132))
The rapid emergence of graphene has attracted numerous efforts to explore other two-dimensional materials. Here, we combine first-principles calculations and Boltzmann theory to investigate the structural, electronic, and thermoelectric transport properties of monolayer C3N, which exhibits a honeycomb structure very similar to graphene. It is found that the system is both dynamically and thermally stable even at high temperature. Unlike graphene, the monolayer has an indirect band gap of 0.38 eV and much lower lattice thermal conductivity. Moreover, the system exhibits obviously larger electrical conductivity and Seebeck coefficients for the hole carriers. Consequently, the ZT value of p-type C3N can reach 1.4 at 1200 K when a constant relaxation time is predicted by the simple deformation potential theory. However, such a larger ZT is reduced to 0.6 if we fully consider the electron-phonon coupling. Even so, the thermoelectric performance of monolayer C3N is still significantly enhanced compared with that of graphene, and is surprisingly good for low-dimensional thermoelectric materials consisting of very light elements.
A low cost, non-toxic and highly selective catalyst based on a Cu-lignin molecular complex is developed for CO2 electroreduction to ethanol. Ni foam (NF), Cu-Ni foam (Cu-NF) and Cu-lignin-Ni foam (Cu-lignin-NF) were prepared by a facile and reproducible electrochemical deposition method. The electrochemical CO2 reduction activity of Cu-lignin-NF was found to be higher than Cu-NF. A maximum faradaic efficiency of 23.2 % with current density of 22.5 mA cm-2 was obtained for Cu-lignin-NF at -0.80 V (vs. RHE) in 0.1 M Na2SO4 towards ethanol production. The enhancement of catalytic performance is attributed to the growth of the number of active sites and the change of oxidation states of Cu and NF due to the presence of lignin.
Due to the high demand for more convenient flexible devices, there are more requirements for higher performance of flexible batteries. The layered lithium-rich manganese-based Li1.2Ni0.13Co0.13Mn0.54O2 cathode material has the advantages of higher energy density, higher discharge capacity and environmentally friendly, so it can be used for high-performance flexible electrode cathode material. Its theoretical capacity can reach more than 250mAh g-1, which is higher than most cathode materials currently used in commercialization. Here we synthesize Li1.2Ni0.13Co0.13Mn0.54O2 (LNCM) cathode, and then use a simple method to make a current collect-free LNCM flexible film. This film has excellent flexibility and electrochemical performance. At 25 mA g-1, its initial discharge capacity reaches 314.0 mAh g-1. After 200 cycles of 500 mA g-1, its capacity retention rate is 82.1%, the attenuation is about 0.08% per cycle. Moreover, by bending at any position of the flexible film, it can still remain intact, and the soft-packaged battery made by the flexible film can still be used under the bending condition and keep the brightness of the LED lamp unchanged. This shows that using Li1.2Ni0.13Co0.13Mn0.54O2 to make high-performance flexible electrodes is a simple and effective method, which is expected to be practically applied to flexible electronic devices.
A novel plasmonic structure is demonstrated by combining graphene with a planar LiNbO3 thin layer, which is simple and easy to fabricate compared to the complex design of general graphene surface plasmons devices. Graphene from the chemical vapor deposition is investigated and characterized to be a continuous and uniform monolayer or fewlayer. LiNbO3 capped by graphene layer show an extraordinary absorption enhancement in an attenuated total reflection (ATR) measurement at a wide bandwidth of 500~4000 cm-1, which can be explained by resonance absorption resulting from the coupling of graphene surface plasmons with optical modes of LiNbO3-SiO2 Fabry-Perot cavity and LiNbO3 planar waveguide. The simulation results are generally consistent with the ATR experimental results. The absorption spectra versus temperature of this plasmonic configuration is also investigated, which show that increasing the testing temperature not only highlights the atomic vibrational peaks of graphene, but also enhances the absorption at several characteristic absorption frequencies due to the enhanced coupling between the surface plamons excitations and the optical modes.
Peptide-based supramolecular self-assembly from peptide monomers into well-organized nanostructures, has attracted extensive attentions towards biomedical and biotechnological applications in recent decades. This spontaneous and reversible assembly process involving non-covalent bonding interactions can be artificially regulated. In this review, we have elaborated different strategies to modulate the peptide self-assembly through tuning the physicochemical and environmental conditions, including pH, light, temperature, solvent, and enzyme. Detailed introduction of biological applications and future potential of the peptide-based nano-assemblies will also be given.
Nanotechnology, Volume 32; https://doi.org/10.1088/1361-6528/ac28d7
The effect of organic solvents on the ion track-etching of polyimide (PI) membranes is studied to enhance the nanopore fabrication process and the control over pore diameter growth. To this end, two approaches are employed to investigate the influence of organic solvents on the nanopore fabrication in PI membranes. In the first approach, the heavy ion irradiated PI samples are pretreated with organic solvents and then chemically etched with sodium hypochlorite (NaOCl) solution, resulting up to ~4.4 times larger pore size compared to untreated ones. The second approach is based on a single-step track-etching process where the etchant (NaOCl) solution contains varying amounts of organic solvent (by vol%). The experimental data shows that a significant increase in both the bulk-etch and track-etch rates is observed by using the etchant mixture, which leads to ~47% decrease in the nanopore fabrication time. This enhancement of nanopore fabrication process in PI membranes would open up new opportunities for their implementation in various potential applications.
Domain switching pathways in ferroelectric materials visualized by dynamic Piezoresponse Force Microscopy (PFM) are explored via variational autoencoder (VAE), which simplifies the elements of the observed domain structure, crucially allowing for rotational invariance, thereby reducing the variability of local polarization distributions to a small number of latent variables. For small sampling window sizes the latent space is degenerate, and variability is observed only in the direction of a single latent variable that can be identified with the presence of domain wall. For larger window sizes, the latent space is 2D, and the disentangled latent variables can be generally interpreted as the degree of switching and complexity of domain structure. Applied to multiple consecutive PFM images acquired while monitoring domain switching, the polarization switching mechanism can thus be visualized in the latent space, providing insight into domain evolution mechanisms and their correlation with the microstructure.
We demonstrate the conversion to quasi two-dimensional (2D) β-Ga2O3 by thermally oxidizing layered GaSe of different thicknesses (from bilayer to 100 nm). GaSe flakes were prepared by mechanical exfoliation onto Si with a 300 nm SiO2 layer, highly oriented pyrolytic graphite (HOPG), and mica substrates. The flakes were then annealed in ambient atmosphere at different temperatures ranging from 600°C to 1000°C for 30 min. Raman spectroscopy confirmed the formation of β-Ga2O3 in the annealed samples by comparison with the Raman spectrum of a β-Ga2O3 reference crystal. Atomic force microscopy was employed to study the morphology and the thickness of the β-Ga2O3 flakes. In addition, we used energy dispersive Xray spectroscopy together with scanning electron microscopy to investigate the evolution of the composition, especially Se residuals, and the sample topography with annealing temperature. β-Ga2O3 appears at temperatures above 600°C and Se is completely evaporated at temperatures higher than 700°C. The thicknesses of the resulting β-Ga2O3 flakes are half of that of the initial GaSe flake. Here we therefore present a straightforward way to prepare 2D β-Ga2O3 by annealing 2D GaSe.
LiNi0.8Co0.15Al0.05O2 (NCA), a promising ternary cathode material of lithium-ion batteries, has widely attracted attention due to its high energy density and excellent cycling performance. However, the presence of residual alkali (LiOH and Li2CO3) on the surface will accelerate its reaction with HF from LiPF6, resulting in structural degradation and reduced safety. In this work, we develop a new coating material, LiH2PO4, which can effectively optimize the residual alkali on the surface of NCA to remove H2O and CO2 and form a coating layer with excellent ion conductivity. Under this strategy, the coated sample [email protected] (P2-NCA) provides a capacity of 147.8 mAh/g at a high rate of 5C, which is higher than the original sample (126.5 mAh/g). Impressively, the cycling stabilities of P2-NCA under 0.5 C significantly improved from 85.2 % and 81.9 % of pristine-NCA cathode to 96.1 % and 90.5 % at 25 ℃ and 55 ℃, respectively. These satisfied findings indicate that this surface modification method provides a feasible strategy toward improving the performance and applicability of nickel-rich cathode materials.
In Part I of this topical review, we discussed dynamical phenomena in nanomagnets, focusing primarily on magnetization reversal. In this part, we address mostly wave-like phenomena in nanomagnets, with emphasis on spin waves in myriad nanomagnetic systems and methods of controlling magnetization dynamics in nanomagnet arrays. We conclude with a discussion of some interesting spintronic phenomena that undergird the rich physics exhibited by nanomagnet assemblies.
Nanotechnology, Volume 32; https://doi.org/10.1088/1361-6528/ac297f
The modulation p-doping technique has emerged as an effective way to optimize the carrier dynamics process of quantum dot (QD) structures. Here, the laser structures based on the 1.3 μm multiple-layer InAs/GaAs QD were fabricated with and without modulation p-doping. The carrier relaxation rate was increased after modulation p-doping, as demonstrated by transient absorption spectroscopy. The higher relaxation rate in p-doped QDs could be explained by more rapid carrier-carrier scattering process originating from increasing of the hole quasi-Fermi-level movement that increases the probability of occupancy of the valence states. In addition, the lasing behavior of Fabry-Perot lasers with and without modulation p-doping was investigated and compared. It was found that the ground state (GS) lasing in the absence of facet coating was successfully achieved in a p-doped laser diode with short cavity length (400 μm), which can be attributed to the higher GS saturation gain caused by p-doping. With assistance of a designed TiO2/SiO2 facet coating whose central wavelength (~1480 nm) is far beyond the lasing wavelength of 1310 nm, the GS lasing could be realized in a laser diode with short cavity lengths (300 μm) under continuous wave operation at room temperature, implying great potential for the development of low-cost and high-speed directly modulated lasers.
The van der Waals(vdW) heterostructures formed by stacking layered two-dimensional materials can improve the performance of materials and provide more applications. In our paper, six configurations of AlN/MoS2 vdW heterostructures were constructed, the most stable structure was obtained by calculating the binding energy. On this basis, the effect of external vertical strain on AlN/MoS2 heterostructure was analyzed, the calculated results show that the optimal interlayer distance was 3.593Å and the band structure was modulated. Then the h-BN intercalation was inserted into the AlN/MoS2 heterostructure, by fixing the distance between h-BN and AlN or MoS2, two kinds of models were obtained. Furthermore, the electronic properties of AlN/MoS2 heterostructure can be regulated by adding h-BN intercalation layer and adjusting its position. Finally, the optical properties show that the absorption coefficient of AlN/MoS2 heterostructure exhibits enhancement characteristic compared with that of the individual monolayers. Meantime, compared with AlN/MoS2, the AlN/h-BN/MoS2 shows a redshift effect and the light absorption peak intensity increased, which indicated that h-BN intercalation layer can be used to regulate the electronic and optical properties of AlN/MoS2 heterostructure.
Nanowires (NWs) with a unique one-dimensional structure can monolithically integrate high-quality III-V semiconductors onto Si platform, which is highly promising to build lasers for Si photonics. However, the lasing from vertically-standing NWs on silicon is much more difficult to achieve compared with NWs broken off from substrates, causing significant challenges in the integration. Here, the challenge of achieving vertically-standing NW lasers is systematically analysed with III-V materials, e.g. GaAs(P) and InAs(P). The poor optical reflectivity at the NW/Si interface results severe optical field leakage to the substrate, and the commonly used SiO2 or Si2N3 dielectric mask at the interface can only improve it to ~10%, which is the major obstacle for achieving low-threshold lasing. A NW super lattice distributed Bragg reflector is therefore proposed, which is able to greatly improve the reflectivity to >97%. This study provides a highly-feasible method to greatly improve the performance of vertically-standing NW lasers, which can boost the rapid development of Si photonics.
In this paper, we study the property changes in TiO2 thin films related to annealing under various conditions. XPS analysis showed that the concentration of oxygen vacancies in TiO2 thin films was reduced by annealing. In the case of annealing in an O2 and air atmosphere, the oxygen vacancy concentration was reduced to the greatest extent as oxygen diffused into the TiO2 thin film and rearrangement of atoms occurred. XRD analysis showed that the anatase structure of annealed TiO2 thin films was clearly present compared to the as-deposited TiO2 thin film. I-V analysis showed that the lower the concentration of oxygen vacancy, the lower the leakage current (O2 annealed TiO2 : 10-4A/cm2) than as dep TiO2 thin film(~10-1A/cm2). The dielectric constant of annealed TiO2 thin films was 26-30 which was higher than the as-deposited TiO2 thin film (k~18) because the anatase structure became more apparent.
The development of simple, scalable, and cost-effective methods to prepare Van der Waals materials for thermoelectric applications is a timely research field, whose potential and possibilities are still largely unexplored. In this work, we present a systematic study of ink-jet printing and drop-casting depositionof 2H-phase SnSe2 and WSe2 nanoflake assemblies, obtained by liquid phase exfoliation, and their characterization in terms of electronic and thermoelectric properties. The choice of optimal annealing temperature and time is crucial for preserving phase purity and stoichiometry and removing dry residues of ink solvents at inter-flake boundaries, while maximizing the sintering of nanoflakes. An additional pressing is beneficial to improve nanoflake orientation and packing, thus enhancing electric conductivity. In nanoflake assemblies deposited by drop casting and pressed at 1 GPa, we obtained thermoelectric power factors at room temperature up to 2.2x10-4 mW m-1 K-2 for SnSe2 and up to 3.0x10-4 mW m-1 K-2 for WSe2.
Ag/SiO2 and Au/SiO2 samples were prepared by separately implanting 30 keV Ag and Au ions into 0.5-mm-thick SiO2 slabs at a fluence of 6 × 1016 ion/cm2, and their optical and structural properties were studied in detail by using a fiber spectrometer and a transmission electron microscope, respectively. Our results showed that the two samples featured by their respective nanocomposite surface layers were asymmetrical in structure, and hence, their characteristic signals in the reflectance spectra excited by the lights incident from the rear surfaces were able to exhibit corresponding blueshifts when the overlays on the implanted surfaces were increased in refractive index with respect to air. Our results also showed that each of characteristic signals was strongly dependent on the localized surface plasmon resonance (LSPR) behavior of the involved Ag or Au nanoparticles (NPs), and it could not appear at a wavelength position smaller than or equal to that of the LSPR absorption peak since the involved Ag or Au NPs were quite small in size. These results meant that the two samples could be regarded as the LSPR sensors with a negative refractive index sensitivity (RIS), although their sensing abilities would lose when the overlays were very large in refractive index. Especially, the two samples were demonstrated to be relatively high in stability because the involved Ag and Au NPs were closely hugged and chemically protected by the matrices of SiO2, and consequently, they could have a chance to become prospective sensing devices in some special fields as long as their RISs and linearities could be improved in the future. The above findings substantially confirmed that the metal ion implantation into transparent dielectric slab was an effective route to the high-stability LSPR sensors.
Fluorescent carbon dots (CDs) have attracted considerable interest due to their superior optical properties and facile preparation. In this work, O-phenylenediamine and melamine were used as precursors for the one-step hydrothermal synthesis of novel orange emissive carbon dots (O-CDs) in an aqueous solution. The fluorescence intensity (580 nm) of the O-CDs exhibited a good linear relationship with Ag+ in the range of 0.0-50.0 μM with the detection limit of 0.289 μM. Moreover, the O-CDs were successfully used to determine Ag+ in biological samples (Hela cells) because of their low cytotoxicity, and good biocompatibility. Besides, the O-CDs-doped solid-phase detection materials (test paper and hydrogel) were employed to monitor Ag+ qualitatively and quantitatively, indicated that the O-CDs had a great capacity for the detection of Ag+ in biological and environmental areas. Based on their extraordinary fluorescence property, the O-CDs could also be used as security ink. Overall, based on their excellent fluorescent performance, the CDs in this study have significant potential for practical application toward solid-phase sensing and security ink.
When magnets are fashioned into nanoscale elements, they exhibit a wide variety of phenomena replete with rich physics and the lure of tantalizing applications. In this topical review, we discuss some of these phenomena, especially those that have come to light recently, and highlight their potential applications. We emphasize what drives a phenomenon, what undergirds the dynamics of the system that exhibits the phenomenon, how the dynamics can be manipulated, and what specific features can be harnessed for technological advances. For the sake of balance, we point out both advantages and shortcomings of nanomagnet based devices and systems predicated on the phenomena we discuss. Where possible, we chart out paths for future investigations that can shed new light on an intriguing phenomenon and/or facilitate both traditional and non-traditional applications.
Nanotechnology, Volume 32; https://doi.org/10.1088/1361-6528/ac28dc
Developing green materials applied in lithium-ion batteries is of significant importance for the present-day society. Herein, a feasible strategy to construct Fe3O4 nanoparticles (NPs) embedded in 3D honeycomb biochar derived from pleurotus eryngii was proposed. The obtained material consists of Fe3O4 NPs (35~85 nm) encapsulated in 3D honeycomb biochar possesses a high specific capacity of 723 mAh g-1 at 1.5 A g-1 after 1000 cycles. The effectively enhanced cycling life of [email protected] nanocomposites can be ascribed to the small Fe3O4 NPs provide lower degree of cracking and high specific capacity, while the honeycomb biochar function like a cage to inhibit huge volume change of Fe3O4 NPs during the charge-discharge process.
Perovskites, garnets, monoclinic forms, and lately also oxyhydroxides doped with rare earth ions have been drawn large attention due to their beneficial optical and photovoltaic properties. In this work we have shown that several forms of crystals from Y-Al-O family can be synthesized using microwave driven hydrothermal technique using different pH and post-growth annealing at different temperatures. The structural and optical properties of these crystals were investigated as a function of hydrothermal crystallization conditions. X-ray diffraction, scanning electron microscopy, and the photoluminescence studies were performed. All the structures have been doped with Eu3+ ions which are known as a local symmetry sensor, because various symmetries generate different crystal fields and thus affect their luminescence spectra. Optical properties of the obtained nanoparticles in correlation with their structure and chemical composition are discussed.
Rapid and sustained disinfection of surfaces is necessary to check communicability of microbial. The current study proposes a method of synthesis and use of copper nanoparticles (CuNP) for contact disinfection of pathogenic microorganisms. Polyphenol stabilized CuNP were synthesized by successive reductive disassembly and reassembly of copper phenolic complexes. Morphological and compositional characterizations by transmission electron microscopy (TEM), selected area diffraction and electron energy loss spectroscopy reveal monodispersed spherical (ϕ 5-8 nm) copper nanoparticles with coexisting Cu, Cu(I) and Cu(II) phases. Various commercial grade porous and non-porous substrates, such as, glass, stainless steel, cloth, plastic and silk were coated with the nanoparticles. Complete disinfection of 107 copies of surrogate enveloped and non-enveloped viruses: bacteriophage MS2, SUSP2, phi6; and gram negative as well as gram positive bacteria: E.coli and S.aureus was achieved on most substrates within minutes. Structural cell damage was further analytically confirmed by TEM. The formulation was well retained on woven cloth surfaces even after repeated washing, thereby revealing its promising potential for use in biosafe clothing. In the face of the current pandemic, the nanomaterials developed are also of commercial utility as an eco-friendly, mass producible alternative to bleach and alcohol based public space sanitizers used today
Nanotechnology, Volume 32; https://doi.org/10.1088/1361-6528/ac232d
As a two-dimensional (2D) layered semiconductor, lead iodide (PbI2) has been widely used in optoelectronics owing to its unique crystal structure and distinctive optical and electrical properties. A comprehensive understanding of its optical performance is essential for further application and progress. Here, we synthesized regularly shaped PbI2 platelets using the chemical vapor deposition method. Raman scattering spectroscopy of PbI2 platelets was predominantly enhanced when the laser radiated at the edge according to Raman mapping spectroscopy. Combining the outcome of polarized Raman scattering spectroscopy and finite-difference time-domain simulation analysis, the Raman enhancement was proven to be the consequence of the enhancement effects inherent to the high-refractive-index contrast waveguide, which is naturally formed in well-defined PbI2 platelets. Because of the enlarged excited area determined by the increased propagation length of the laser in the PbI2 platelet formed waveguide, the total Raman enhancements are acquired rather than a localized point enhancement. Finally, the Raman enhancement factor is directly related to the thickness of the PbI2 platelet, which further confirms the waveguide-enhanced edge Raman. Our investigation of the optical properties of PbI2 platelets offers reference for potential 2D layered-related optoelectronic applications.
A systematic interpretation of the undoped and Fe doped ZnO based multifunctional sensor developed employing economic and facile low-temperature hydrothermal method is reported. The tailoring of the performance improvement of the sensor was deliberately carried out using varied concentration (1, 3 and 5 Wt%) of Fe dopant in ZnO nanorods. The structural and morphological analysis reveal the undisturbed ZnO hexagonal wurtzite structure formation and 1D morphology grown even when the dopant is added. The optical property study evidences a decreased bandgap (3.10 eV) and decreased defects of 5 Wt% of Fe dopant in ZnO nanorods based sensor compared to the undoped one. The electrical process transpiring in the tailored multifunctional sensor is investigated using photoconductivity and impedance analysis elucidates proper construction of p-n junction between the piezoelectric n-type active layer (undoped and Fe doped ZnO nanorods) and p-type PEDOT: PSS ((poly(3,4-ethylene dioxythiophene) polystyrene sulfonate)) and reduced internal resistance of 5 Wt% of Fe dopant in ZnO nanorods based sensor (131.97Ω) respectively. The investigation on the experimental piezoelectric acceleration and gas sensing validation and the performance measurement were interpreted using test systems. A revamped output voltage of 3.71 V for 1g input acceleration and a comprehensive sensitivity of 7.17 V/g was achieved for the 5 Wt% of Fe dopant in ZnO nanorods based sensor sensor. Similarly, an upgraded sensitivity of 2.04 and 6.75 for 5 Wt% of Fe dopant in ZnO nanorods based sensor was obtained when exposed to 10 ppm of target gases namely CO and CH4 respectively at room temperature. Appending to this, acceptable stability of the sensor for both the sensing (acceleration and gas) was also attained manifesting its prospective application in multifunctional based systems like sewage systems.
The 1T/2H hybridized and 2H pure phases of MoS2 nanoflowers were synthesized in a one-step hydrothermal process with the molybdenum source as sodium molybdate dihydrate and the sulfur source as thiourea. The as-prepared 1T/2H hybridized and of 2H pure phases of MoS2 were investigated using a thermogravimetry\differential thermal analysis (TG\DTA), powder X-ray diffraction (P-XRD), field emission scanning electron microscopy (FESEM), and energy-dispersive X-ray (EDX) spectroscopy. The obtained 1T/2H hybridized phases of MoS2 were confirmed by the Raman spectroscopy. The electrochemical characteristics of MoS2 electrodes were examined using cycle voltammetry (CV), galvanostatic charge-discharge (GCD) and electrochemical impedance spectroscopy (EIS). The electrodes based on the 1T/2H hybridized phases MoS2 with specific capacitance (Cp) of 555.4 F g-1 at current densities (Cd) of 0.5Ag-1, capacity retention ratio of 85.7% after 3000 cycle were observed that could be a strong potential electrode material for supercapacitors application.
The prospects of the development of non-volatile memory elements that involve memristive metal-dielectric-metal sandwich structures are due to the possibility of reliably implementing sustained functional states with quantized conductance. In the present paper, we have explored the properties of Zr/ZrO2/Au memristors fabricated based on an anodic zirconia layer that consists of an ordered array of vertically oriented non-stoichiometric nanotubes with an outer diameter of 30 nm. The operational stability of the designed memory devices has been analyzed in unipolar and bipolar resistive switching modes. The resistance ratio ≧105 between high-resistance (HRS) and low-resistance (LRS) states has been evaluated. It has been found that the LRS conductivity is quantized over a wide range with a fundamental minimum of 0.5G0 = 38.74 µS due to the formation of quantum conductors based on oxygen vacancies (V0). For Zr/ZrO2/Au memristors, resistive switching mechanisms to be sensitive to the migration of VO in an applied electric field have been proposed. It has been shown that the ohmic type and space-charge-limited conductivities are realized in the LRS and HRS, respectively. Besides, we have offered a brief review of parameters for functional metal/zirconia/metal nanolayered structures to create effective memristors with multiple resistive states and a high resistance ratio.
Electronic sensors for volatile organic compounds have been prepared by drop-casting dispersions of multi-wall carbon nanotubes in aqueous solutions of λ-DNA onto Pt microband electrodes. The MWCNTs themselves show a metal-like temperature dependence of the conductance, but the conductance of DNA/MWCNT composites has an activated component that corresponds to inter-tube tunneling. The resistance of the composite was modelled by a series combination of a term linear in temperature for the nanotubes and a stretched exponential form for the inter-tube junctions. The resistance may increase or decrease with temperature according to the composition and may be tuned to be almost temperature-independent at 67% by mass of DNA. Upon exposure to organic vapours, the resistance of the composites increases and the time-dependence of this signal is consistent with diffusion of the vapour into the composite. The fractional change in resistance at steady-state provides an analytical signal with a linear calibration and the presence of DNA enhances the signal and adjusts the selectivity in favour of polar analytes. The temperature dependence of the signal is determined by the enthalpy of adsorption of the analyte in the inter-tube junctions and may be satisfactorily modelled using the Langmuir isotherm. Temperature and pressure-dependent studies indicate that neither charge injection by oxidation/reduction of the analyte nor condensation of analyte on the device is responsible for the signal. We suggest that the origin of the sensing response is an adsorption of the analyte in the inter-tube regions that modulates the tunneling barriers. This suggests a general route to tuning the selectivity of multi-wall carbon nanotube gas sensors using non-conductive polymers of varying chemical functionality.
This work illustrates the most effective way of utilizing the ferroelectricity for tunnel field-effect transistors (TFETs). The ferroelectric (Hf0.5Zr0.5O2) in shunt with gate-dielectric is utilized as an optimized metal-ferroelectric-semiconductor (OMFS) option to improve the internal voltage (Vint) for ample utilization of polarization and electric fields of Hf0.5Zr0.5O2 across the tunneling region. The modeling of Vint signifies 15-20% and 5% reduction in tunneling length (λ) and energy barrier width (Δφ) than the nominal metal-ferroelectric-insulator-semiconductor (MFIS) options. Furthermore, the TFET geometry with the scaled-epitaxy region as vertical TFET (VTFET), strained Si0.6Ge0.4 as source, and gate-all-around nanowire options are used as an added advantage for further enhancement of TFET's performance. As a result, the proposed design (OMFS-VTFET) achieves superior DC and RF performances than the MFIS option of ferroelectric. The figure of merits in terms of DC characteristics in the proposed and optimized structure are of improved on-current (= 0.23 mA/μm), high on-to-off current ratio (= 1011), steep subthreshold swing (= 33.36 mV/dec), and superior unity gain cut-off frequency (≥ 300 GHz). The design is revealed as energy efficient with 2-to-3 order reduction of energy-efficiency in both logic and memory applications.
Nanotechnology, Volume 32; https://doi.org/10.1088/1361-6528/ac28d6
Ion irradiation of bulk and thin film materials is tightly connected to well-described effects such as sputtering or/and ion beam mixing. However, when a nanoparticle is ion irradiated and the ion range is comparable to the nanoparticle size, these effects are to be reconsidered essentially. This study investigates the morphology changes of silver nanoparticles on top of silicon substrates, being irradiated with Ga+ ions in an energy range from 1 to 30 keV. The hemispherical shaped nanoparticles become conical due to an enhanced and curvature-dependent sputtering, before they finally disappeared. The sputter yield and morphology changes can be well described by 3D Monte-Carlo TRI3DYN simulations. However, the combination of sputtering, ion beam mixing, ion beam induced diffusion, and Ostwald ripening at low ion energies results in the reappearance of new particles. These newly formed nanoparticles appear in various structures depending on the material and ion energy.
Nanotechnology, Volume 32; https://doi.org/10.1088/1361-6528/ac2810
Silicon film is an attractive anode candidate in lithium-ion batteries (LIBs) due to its two-dimensional (2D) morphology that is beneficial to buffer the large volume expansion of traditional silicon anodes. Even so, the generation of stress during the lithiation/delithiation process can still lead to the cracking and delamination of the silicon film from the current collector, ultimately resulting in the fast failure of the electrode. Laying a graphene layer between the silicon film and the current collector has been demonstrated to alleviate the stress generated during the battery cycling, but its universal application in commercial silicon structures with other dimensionalities remains technically challenging. Putting graphene on top of a 2D silicon film is more feasible and has also been shown with enhanced cycling stability, but the underneath mechanical mechanisms remain unclear. Herein, using the combination of 2D graphene and 2D silicon films as a model material, we investigate the stress generation and diffusion mode during the battery cycling to disclose the mechanical and electrochemical optimization of a silicon anode experimentally and theoretically. As a result, the optimum thickness of the silicon film and the coated graphene layers are obtained, and it is found the in-plane cracking and out-of-plane delamination of the silicon film could be mitigated by coating graphene due to the slow transfer of the normal and shear stresses. This work provides some understanding of the electrochemically derived mechanical behaviors of the graphene-coated battery materials and guidelines for developing stable high-energy-density batteries.
Recently, antimony-doped tin oxide nanoparticles (ATO NPs) have been widely used in the fields of electronics, photonics, photovoltaics, sensing, and other fields because of their good conductivity, easy synthesis, excellent chemical stability, high mechanical strength, good dispersion and low cost. Herein, for the first time, a novel nonvolatile transistor memory device is fabricated using ATO NPs as charge trapping sites to enhance the memory performance. The resulting organic nano-floating gate memory (NFGM) device exhibits outstanding memory properties, including tremendous memory window (~85 V), superhigh memory on/off ratio (~10^9), long data retention (over 10 years) and eminent multilevel storage behavior, which are among the optimal performances in NFGM devices based on organic field effect transistors. Additionally, the device displays photoinduced-reset characteristic with low energy consumption erasing operation. This study provides novel avenues for the manufacture of simple and low-cost data storage devices with outstanding memory performance, multilevel storage behavior and suitability as platforms for integrated circuits.
Nanotechnology, Volume 32; https://doi.org/10.1088/1361-6528/ac22df
Nanotechnology, Volume 32; https://doi.org/10.1088/1361-6528/ac2848
Nanotechnology, Volume 32; https://doi.org/10.1088/1361-6528/ac238f
Nanotechnology, Volume 32; https://doi.org/10.1088/1361-6528/ac2846